The present invention relates in general to electronic devices, and, more particularly, to devices which can detect non-intermittent short-circuits towards ground and towards a supply.
There is a need to detect, at an input terminal, the presence of a short-circuit towards ground or towards the supply. The short-circuit indication should avoid indicating intermittent or partial short-circuits. The term xe2x80x9cshort-circuitxe2x80x9d is intended to indicate a connection having a resistance equal to or less than a given value (for example, 20 Kohms). Circuits of this type, which can perform the aforementioned functions, accurately and reliably and which, at the same time, are simple and inexpensive, are not known in the art.
The object of the present invention is to provide a circuit for detecting short-circuits, which overcomes the problems indicated above in a satisfactory manner.
According to the present invention, this object is achieved by means of a circuit for detecting short-circuits comprising current-generating means for generating a current of predetermined intensity selectively into or out of a desired terminal. The device may also include first voltage-comparator means connected to the desired terminal and connected to the current-generating means in a manner such that the current-generating means generates a current in the inward direction and in the outward direction relative to the desired terminal when a voltage between the desired terminal and ground is greater than a first level and less than a second level, respectively, the first level being greater than or equal to the second level. In addition, the device preferably includes second voltage-comparator means for supplying a first and a second signal, respectively, when the voltage between the desired terminal and ground is close to the direct-current supply voltage and close to ground, respectively. Processing-circuit means may be connected to the second comparator means for detecting whether the first or the second signal, respectively, lasts for a predetermined period of time and, responsive thereto, for supplying an output signal indicative of a short-circuit of the terminal towards the supply or towards ground, respectively.